As an example of a technology to manage one or more objects to be managed, a bar code system using bar codes has been known. Objects to be managed may be goods, merchandise, documents, or any other arbitrary objects. The bar code system reads a bar code attached on an object to be managed by a bar code reader, and obtains information represented by the bar code. However, the bar code system needs to read bar codes one by one, and it is not easy to collectively manage or to process lots of objects to be managed at once.
A RFID tag system using RFID (Radio Frequency IDentification) tags can cope with such a concern, in theory. An RFID tag is also called an “RFIC (Radio Frequency Integrated Circuit) tag” or a “wireless tag”. In an RFID tag system, a RFID tag reader transmits a radio wave, and then, a RFID tag that receives the radio wave transmits information stored in its own memory. The RFID tag reader obtains information transmitted from a number of RFID tags to collectively manage the RFID tags (Non-Patent Documents 1-2).